Check iOS selector availability

gistfile1.m

// Check for the existence of a selector
	if ([_pageControl respondsToSelector:@selector(pageIndicatorTintColor)] == YES) {
	}
	

// Check device system version
	+ (BOOL)isRunningiOS5 {
	
	   // This will only return true in iOS 5 and up.
	   if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 5.0f) {
	       return YES;
	   } else {
	       return NO;
	   }
	}